Electronics 01
Why Do Blue LEDs Need More Voltage Than Red?
Blue photons carry 0.8 eV more than red ones, yet blue LEDs need 1.45 V more. Datasheets show where the extra voltage goes and why white LEDs match blue.
electronics
Electronics 02
Why Is Three-Phase Power Used? The Real Reasons
Three-phase power delivers constant power and a rotating field for motors. The copper saving is real but depends on what you compare. Worked numbers here.
Electronics 03
LC Resonant Frequency Formula: Derivation, Q and Real Parts
f = 1/(2π√LC), derived from energy sloshing, with Q, bandwidth, an AM tuner worked example, and why real coils and capacitors miss the ideal number.
Electronics 04
How Do Noise Cancelling Headphones Work? The Timing Math
Noise cancelling headphones play inverted sound, but a 20° phase error leaves a third of the noise. Why ANC kills engine drone and not voices, with plots.
Electronics 05
How Does an H-Bridge Work? Decay, Dead Time, Losses
Four switches reverse a motor, but the details decide whether it works: shoot-through and dead time, brake vs coast, why an L298 loses 2.5 V and PWM ripple.
Electronics 06
How Does a Boost Converter Work? Worked 3.7 V to 5 V
How a boost converter stores energy in an inductor and releases it at higher voltage. Worked 3.7 V to 5 V design, and why D near 1 fails.
Electronics 07
Why Do Transformers Hum? It's 100 or 120 Hz, Not 50 or 60
Transformer hum comes from magnetostriction: the core stretches about 2 micrometres per metre twice every cycle. Why 100/120 Hz, and what makes it louder.
Electronics 08
Why 100nF Decoupling Capacitors? The Impedance Math
Why is every decoupling capacitor 100 nF? Impedance plots with ESL and via inductance show what the value really does and when 1 µF is better.
Electronics 09
Can You Use a Voltage Divider as a Power Supply?
A 7 kΩ / 5 kΩ divider makes 5 V from 12 V until you load it: at 20 mA it gives 0.39 V. The Thevenin math, the efficiency limit, and when a divider is fine.
Electronics 10
Relay Flyback Diode: Why You Need One and Which to Use
A relay coil can kick back 1,000 V at turn-off. A flyback diode stops it but slows contact release about 5x. Here is the math and the diode plus zener fix.
Electronics 11
Why Is the RC Time Constant 63%? The Math of 1 − 1/e
63.2% is 1 minus 1/e, the point where an RC curve would have finished if it kept its starting slope. Why e appears, and why 5τ is not always enough.
Electronics 12
RC Low Pass Filter Cutoff Frequency: What −3 dB Means
fc = 1/(2πRC) is where the output is 0.707 of the input, half power and −45°. Why the slope there is only 10 dB/decade, and how loading moves it.
Electronics 13
How to Choose a Pull-Up Resistor Value (With I2C Math)
Pull-up resistors have a minimum set by sink current and a maximum set by rise time and leakage. Worked I2C example at 400 kHz, plus MCU internal pull-ups.
Electronics 14
MOSFET Gate Resistor Value: How to Choose It (With Math)
The gate loop is a series RLC circuit. Choose the gate resistor for damping 0.7 to 1, then check switching loss and pin current. Worked IRLZ44N example.
Electronics 15
How Does a Buck Converter Work? Worked 12 V to 3.3 V
How a buck converter works, from volt-second balance to Vout = D·Vin, with a worked 12 V to 3.3 V, 2 A design, computed waveforms and efficiency.
Electronics 16
How to Calculate Crystal Load Capacitors (With Stray C)
CL = C1·C2/(C1+C2) + Cstray, but which stray? Worked 18 pF example, the ppm error from getting it wrong, and the gain margin check most guides skip.
Electronics 17
Button Debounce Capacitor Value: How to Size the RC
Switches bounce for 1.6 ms on average and 6 ms or more at worst. How to size the debounce R and C from Schmitt thresholds, and why 10k with 100 nF is too short.
Electronics 18
555 Timer Frequency Formula: Where 1.44 Comes From
f = 1.44/((R1 + 2R2)C). Why 1.44 is 1/ln 2, why duty cycle can't drop below 50%, and why the diode fix misses 50% at 5 V. Worked 1 kHz example.
Electronics 19
Why Phone Charging Slows After 80%: The CC-CV Curve
Fast charging fills a phone from 0 to 70% at full current, then a fixed voltage limit makes the current taper. The physics, the plating risk and the math.
Electronics 20
Why Is Electricity Transmitted at High Voltage? The Math
Why is electricity transmitted at high voltage? We work the I²R loss for a real 345 kV line, show why 1,100 kV is about the ceiling, and when HVDC wins.
Electronics 21
Why Is AC Power 60 Hz (or 50 Hz)? The Real Tradeoffs
60 Hz came from an 1890 Westinghouse study of engines, lamps and transformers, not Tesla. The physics of transformer size, skin effect and line length.
Electronics 22
LiPo C Rating Explained: Current, Sag and Real Limits
A 5000 mAh 50C LiPo is rated for 250 A, but at 3 milliohms per cell that current sags each cell by 0.75 V. What the C rating means and how to check it.
Electronics 23
Why Is Coax 50 Ohms? The Loss and Power Math
Why is coax 50 ohms? Loss is lowest at 77 Ω, power peaks at 30 Ω, voltage at 60 Ω. Plots of all three, the polyethylene twist, and why TV uses 75 Ω.
Electronics 24
Why Don't Birds Get Electrocuted on Power Lines?
A bird on a live wire feels about 4 millivolts and 4 microamps. We work the numbers, bust the 'not grounded' myth, and show when birds really do die.
Electronics 25
Why Do LEDs Need a Resistor? The I-V Curve Explained
An LED's current rises exponentially with voltage: 0.1 V extra takes a red LED from 20 mA to 56 mA. Here is the physics, the resistor math and the fixes.
Electronics 26
How Does an MPPT Charge Controller Work? Real Curves
A 100 W panel on PWM gives 82 W at 25 °C. MPPT recovers the rest by running a DC-DC converter at the panel's best voltage. When it helps and when not.
Reviews 27
Science gifts for ages 8–12: a Snap Circuits kit or a MEL Science gift plan?
Choose a reusable electronics kit or a prepaid science delivery plan by the child’s interests, adult time and total commitment—with a US gift-plan link and country-specific availability checks.
Projects 28
Building Your Own Quadcopter Drone: Essential Parts and Specifications in India
Drones have captured the imagination of hobbyists, engineers, and professionals alike. Building your own quadcopter drone can be an exciting and rewar